Although there is no built-in feature to create group lists in GMail, there is an easy workaround. Click on Contacts (left-side menu) and choose Add Contact (top right corner). Enter a name for the group in the Name field. Then in the Primary Email field start inputting the addresses of group members. Here is the trick: leave out the first and last brackets. This is how you should do it (substituting the appropriate email addresses):

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Then Save the address. Once you save it, you can see that GMail puts a bracket around the list of addresses. You can try it out by clicking on Compose. Next time you want to send a note to this group, just start typing in the group name and the address list will come up as an option.